Odour control has become an increasingly important feature of absorbent products. Bad smells arising from secretions from the wearer of an absorbent product, or from the storing of bodily fluids within the absorbent product, give easily rise to bad odours which reduces the comfort of the wearer. Thus, it is of high importance that odours can be limited or completely prevented in absorbent products during use.
For prevention of odours one is normally focused on either (1) preventing odours from arising, or (2) preventing odours from escaping out of the absorbent product to the surrounding environment. Several different kinds of odour control agents are known for these purposes.
For instance, for masking odours, fragrances are normally used. For adsorption of odour substances, zeolites, silica, clays, active carbon and/or cyclodextrin amongst others can be used. Some of these tend however to be moisture sensitive. For neutralization of odours, baking soda, citric acid and/or acidic SAP can be used. For inhibition of bacteria growth, copper acetate, SAP with silver and/or acidic SAP can be used. Accordingly, different kinds of odour control agents are effective against different kinds of odour substances, and act with different mechanisms.
As an example EP-A-811389 discloses an absorbent article comprising an odour control system that can be chosen from e.g. silica, zeolite, absorbent gelling material, activated carbon, cyclodextrin and mixtures thereof. The odour control system may be layered on the absorbent core or be mixed within the core. Further, it can be distributed on the edges of the absorbent article.
A common problem with odour control agents is that they tend to be moisture sensitive. For instance, this is the case with zeolites and silica. Accordingly, since absorbent products absorb liquids, it is important that the parts of the absorbent products that become wet still can be effective in controlling odours.
From U.S. Pat. No. 6,147,028 it is known with an odour control agent in the form of polysiloxane-coated starch granules that is used in a sanitary napkin. Polysiloxane is considered to be the active ingredient since it provides a hydrophobic surface.
Further, US2005/0108828 discloses the use of native amylose (a fraction of starch) for odour control of e.g. tobacco or sweat in textiles. Absorbent products are not mentioned in the context of this disclosure. Further, from U.S. Pat. No. 3,622,460 it is known that starch-containing compounds have flavour-retaining properties.
Also, organic volatile substances are important to control in absorbent products, since they have undesired odours.
Moreover, U.S. Pat. No. 5,714,445 discloses articles, such as absorbent articles, comprising small-particle size cyclodextrin (a starch-based compound) for odour control. Cyclodextrin is a cyclic molecule that is composed of 1,4-alpha-linked glucose units. Cyclodextrin can be built up of 6, 7 or 8 glucose units. The inner diameter (the cavity) of cyclodextrin depends on the number of glucose units. This cavity is hydrophobic and form complexes with other substances depending on the size and hydrophobicity of the substance. Also, it will only be capable to take care of complexes when wet. The specific surface area of cyclodextrin is less than 1 m2/g.
Thus, odour control agents for absorbent products need several features to be effective. Moisture-insensitivity to a certain extent, capacity to inhibit various kinds and sizes of odour compounds, not the least hydrophobic compounds, inexpensiveness, capacity to take care of malodours and environmental friendliness are some needs that should be met.